To gain vehicle access, i.e. to unlock a vehicle, a remote key with or without a keyless entry function or an emergency key that still has a conventional key bit is typically used. In either case, unlocking and/or locking of a vehicle door is triggered by a deliberate action performed by a user. With a remote key without keyless entry function, the user presses an unlock button to unlock the motor vehicle or presses a lock button to lock the motor vehicle. When a remote key with the so-called keyless entry function is used, it is sufficient for the user to carry the remote key with him and to touch a sensor surface typically located near the inner surface of a door handle in order to unlock the motor vehicle. When he wishes to lock the motor vehicle again, it is usually sufficient for a user carrying the remote key with keyless entry function to touch a sensor surface located on the outer or upper side of a door handle.
DE 10 2010 061 111 A1 discloses a method in which an operator can use a mobile communication terminal device to activate a motor vehicle locking system, for example to unlock or lock a door of a motor vehicle. For this purpose, it is necessary only for the user to actuate a specific combination of keys on the mobile communication device or to select an element displayed on a screen of the communication device. Thus, the user must actively perform an action on the mobile communication device in order to unlock or lock a motor vehicle.
DE 10 2012 107 000 A1 discloses a method in which a user can use his smartphone to unlock a motor vehicle. In that case, an NFC connection is established between the smartphone and an ID encoder module, as a result of which the smartphone receives an authentication code. The actual unlocking of the motor vehicle takes place via a cellular connection established between the vehicle and the smartphone. This makes it possible to unlock or lock the motor vehicle even from very long distances.
DE 10 2014 107 186 A1 discloses a modular unit having an interface for a communication device, such as a smartphone. The modular unit is therefore a type of adapter which can be attached to the communication device. When the modular unit is held near a vehicle-side communication module, it receives a wake-up signal from a security system of the vehicle. The wake-up signal is transmitted from the modular unit to the communication device, which then transmits a response signal to the security system of the motor vehicle. The transmission of the wake-up signal can be initiated, for example, by the detection of the approach of an operator toward the vehicle by means of a proximity sensor, which is located in an exterior door handle.